Remove redundant attributes

[siriak]

I'm removing those attributes because they are redundant. NUnit can already figure out that those are tests based on TestCase attribute.

• I have performed a self-review of my code
• My code follows the style guidelines of this project
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Comments in areas I changed are up to date
• I have added comments to hard-to-understand areas of my code
• I have made corresponding changes to the README.md

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6922799) 94.50% compared to head (57e9dee) 94.50%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #438   +/-   ##
=======================================
  Coverage   94.50%   94.50%           
=======================================
  Files         234      234           
  Lines        9843     9843           
  Branches     1455     1455           
=======================================
  Hits         9302     9302           
  Misses        381      381           
  Partials      160      160           

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